1. Field of the Invention
The present invention relates to an audio-video stream data recording, replaying, and editing system for recording, replaying, and editing audio-video stream data such as MPEG system stream data in which video data and audio data are mixed with each other.
In recent years, even personal computers of relatively low prices have come to be equipped with a large-capacity hard disk drive. And the prices of encoders for coding analog video and audio according to the MPEG scheme are decreasing.
Further, digital satellite broadcasting services, digital video delivery services using cable television , and like services are spreading.
The above mean that a technical environment that is necessary for general users to record, replay, and edit audio-video entertainment contents that are digital information as they do conventional analog audio and video programs is being established.
With such a variation in environment, a technique that allows general users to record, replay, and edit digital video easily and freely is needed.
2. Description of the Related Art
FIG. 27 shows the configuration of a digital audio-video delivery service system.
In this digital audio-video delivery service system, a video encoder 411 and an audio encoder 412 that are provided in a server 410 encode a video signal and an audio signal according to the MPEG scheme and pass a resulting video elementary stream and audio elementary stream to a multiplexer 413, respectively. The multiplexer 413 is also provided in the server 410.
The multiplexer 413 forms an MPEG system stream by combining the video elementary stream and the audio elementary stream while making adjustments relating to their bit rates. Further, the multiplexer 413 divides the MPEG system stream into packets that are suitable for transmission and pass the MPEG system stream to a transmission device 414 on a packet-by-packet basis.
As shown in FIG. 6, the MPEG system stream formed by the multiplexer 413 is stream data in which GOPs (groups of pictures) that are coding units of the video signal and AAUs (audio access units) that are coding units of the audio signal are mixed with each other according to their bit rates. The MPEG system stream is delivered to terminal devices 420 over a network by the transmission device 414.
Since the amount of MPEG system stream data that is delivered over the network is sufficiently smaller than that of the video data and the audio data before the coding, it is sufficiently realistic to store MPEG system stream data received by a communication controlling section 422 in, for example, a stream data storing section 421 that is provided in each terminal device 420 shown in FIG. 27.
In this case, after the MPEG system stream data is delivered, it can be read out in order from the head from the stream data storing section 421 by a stream data reading section 423 and coded video data and coded audio data can be subjected to replaying processing of an audio-video replaying section 424 when necessary.
A video decoder 425 and an audio decoder 426 that are provided in the audio-video replaying section 424 shown in FIG. 27 decode coded video data and coded audio data that are passed from the stream data reading section 423 and pass decoding results to a display controlling section 427 and an audio replaying section 428, respectively, whereby video and audio are replayed (output) by video/audio output devices such as a CRT display device (denoted by CRT in FIG. 27) 429 and a speaker 430. A user can enjoy the contents that are delivered by this service whenever he wants to do so.
In consideration of the fact that the prices of encoders that conform to the MPEG scheme have decreased, a system is now realistic in which a user captures an analog video signal and audio signal into his own personal computer, coding those signals, and storing resulting data as stream data.
FIG. 28 shows the configuration of an exemplary stream data recording and replaying system.
As shown in FIG. 28, a multiplexer 431 that is provided in a personal computer of a user forms an MPEG system stream by combining a video elementary stream that is received from a video encoder 411 and an audio elementary stream that is received from an audio encoder 412.
While receiving the MPEG system stream, a stream data writing section 432 stores it in a hard disk drive 434 via a disk controlling device 433.
Incidentally, stream data that is stored in this manner in the hard disk drive 434 is basically the same as stream data that is stored in the stream data storing section 421 of the personal computer of a user in the above-described digital audio-video delivery service system. That is, the stream data can be replayed in such a manner that the video and audio are synchronized with each other only when the stream data is read out in order from the head by a stream data reading section 423 and passed to processing of the audio-video replaying section 424.
This is because, as described above, the video signal and the audio signal were coded and compressed independently by the video encoder 411 and the audio encoder 412 with their heads used as references and the resulting elementary streams were combined with each other by the multiplexer 413 in forming the MPEG system stream with their heads used as references, the MPEG system stream being recorded in the hard disk drive 434 as it was.
Therefore, conventionally, the user needs to follow a complex procedure when he edits the video and audio of MPEG system stream data he stored before.
FIG. 29 illustrates a conventional stream data editing operation.
To edit stream data, first, a user needs to replay the entire stream data containing an intended scene via an audio-video replaying section and identify an editing subject scene while watching and hearing outputs of a CRT display device and a speaker.
At this time, an enormous amount of replayed data corresponding to an analog video signal and audio signal needs to be stored for later edit processing.
An edit processing section can edit the data corresponding to the analog video signal and audio signal if receiving a proper edit instruction. However, it is necessary to form an MPEG system stream again based on an editing result with a video encoder, an audio encoder, and a multiplexer (MUX) after completion of an edit operation.
Therefore, in the related art, a stream data editing operation is necessarily accompanied by encoding again an analog video signal and audio signal that were obtained by decoding. And an enormous recording capacity is needed to store data that were needed for the replaying of the analog video signal and audio signal.
The feature of an MPEG system stream as described above restricts a format that is used in recording stream data.
For example, the following method needs to be employed in recording an MPEG system stream that is not limited in length by using a limited storage area, that is, in performing endless recording, in the stream data recording and replaying system of FIG. 28.
Video data and audio data that should form a single stream ordinarily are recorded as a sequence of files of separate stream data having a predetermined short duration (e.g., 10 sec).
This method can realize endless recording by replacing the oldest file with the newest one. However, this method has problems that the file management is complex and the part of replacement cannot be changed freely.